1. Field of Invention
The present invention relates to a cleaning method of a semiconductor structure. More particularly, the present invention relates to a cleaning method of a dual damascene structure.
2. Description of Related Art
When using a dual damascene structure in multilevel metal interconnects, the reliability and process ability of the device are increased. A copper conducting wire is generally used in this process to decrease the resistance of the conducting wire and increase the speed and quality of the integrated circuit device. After the device achieves high integration, using a dielectric layer having a low dielectric constant (low-k) to manufacture the dual damascene structure has gradually become the major technique in the semiconductor industry.
FIG. 1 illustrates a cross-sectional view of a conventional dual damascene structure.
Referring to FIG. 1, a metal layer 102, a cap layer 104 and a dielectric layer 106 are formed on a substrate 100. A dual damascene opening 108 is formed by etching the dielectric layer 106 and cap layer 104. The metal layer 102 serves as an etching stop layer, and a part of the surface of the metal layer 102 is exposed. The material of the cap layer 104 is silicon nitride. This etching process produces a lot of polymer residue that remains on the profile of dual damascene opening 108 and the surface of the metal layer 102. Therefore, a cleaning step can remove the polymer residue and metal oxide on the profile of the dual damascene opening 108 and the surface of the metal layer 102 before a second metal layer fills in the dual damascene opening 108. In the final step, the second metal layer fills in the dual damascene opening 108.
In the conventional cleaning method of the dual damascene opening, an amine-based organic solvent first cleans the dual damascene opening 108, followed by an argon sputtering step to bombard the metal oxide for removing the polymer residue before the second metal layer fills in the dual damascene opening 108. However, the conventional method cannot completely remove the metal oxide from the surface of the metal layer 102. In another conventional cleaning method of dual damascene opening, an amine-based organic solvent cleans as the opening similar to the previous description, and then hydrogen gas (H2) is used to deoxidize the metal oxide for cleaning and removing the polymer residue and the metal oxide. The second cleaning method can completely remove the polymer residues and metal oxide, but the hydrogen also reacts on the dielectric layer 106, and a bow shaped recess 110 is formed, which damages the profile of the dual damascene 108.
The invention provides a cleaning method of a dual damascene to remove the polymer residue and the metal oxide.
The invention also provides a cleaning method of a dual damascene to reduce the via resistance and prevent erosion of the metal layer.
The invention also provides a cleaning method of a dual damascene to prevent further damage on the profile of the dual damascene.
As embodied and broadly described herein, the invention provides a cleaning method of a dual damascene. A first metal layer, a cap layer and a dielectric layer are formed in sequence on a substrate, and then a dual damascene opening is formed in the dielectric layer and the cap layer to expose the surface of the first metal layer. There are two types of cleaning steps after etching. The first method uses a fluorine based organic solvent to clean the dual damascene opening. An alternative cleaning method for the dual damascene opening first uses a hydrogen peroxide based solvent at a high temperature, followed by a hydrofluoric acid solvent cleaning step. Then, an argon gas plasma is sputtered to clean the dual damascene opening before a second metal layer fills in the dual damascene opening.
The cleaning method of this invention is more efficient to remove the polymer residue on the dielectric layer and the metal oxide on the metal layer, and reduces the via resistance in the dual damascene.
The cleaning method of this invention also can prevent further damage on the profile of the dual damascene opening.
The cleaning method of this invention also can prevent the erosion of the metal layer.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.